The present invention relates to apparatus for use in analysing the concentration of nitrogen oxides in a gas.
Apparatuses for analysing nitrogen oxides in gases or in the atmosphere are known. By way of examples, reference may be made to (a) U.K. Patent Specification 1,264,441, (b) an article entitled "Trace Addition of Nitric Oxide and Nitrogen Dioxide to Air by Electrolysis" by P. Hersch and R. Deuringer published in the Journal of the Air Pollution Control Association November 1963 Volume 13 No. 11 P 538-541 and (c) an article entitled "Instrumental Methods for the detection of Higher Oxides of Nitrogen in Nitrous Oxide" by J. T. Shaw published in the British Journal of Anaesthesia (1968) 40 P. 299-303.
These known forms of apparatus are primarily intended for use in the laboratory and necessitate samples of the gas or atmosphere to be collected and brought to the laboratory for analysis.
Apparatus made in accordance with the invention is especially useful for determining the pollution of air or combustion exhaust in situ. The presence of nitrogen oxides in the atmosphere in excess of 5 parts per million is nowadays regarded as harmful. In this context there is a need for a simple reliable rugged apparatus which can be used in the vicinity of combustion equipment, for example, as opposed to a laboratory. A general object of this invention is to provide apparatus which will satisfy this need.